A flexible printed circuit which includes a flexible substrate, a plurality of conductive pads, and a plurality of conductive traces that conductively connect to at least two conductive pads. The plurality of conductive pads and traces are defined on the flexible substrate. The flexible substrate has a first portion and a second portion. The first portion has at least two sets of conductive pads. The second portion has at least one set of conductive pads and is configured to conductively connect to a testing device. After the flexible printed circuit is tested, the second portion of the flexible substrate is detached from the first portion of the flexible substrate.